"use strict";
const Cesium = require("cesium");

const ComponentDatatype = Cesium.ComponentDatatype;

module.exports = getComponentReader;

/**
 * Returns a function to read and convert data from a DataView into an array.
 *
 * @param {number} componentType Type to convert the data to.
 * @returns {ComponentReader} Function that reads and converts data.
 *
 * @private
 */
function getComponentReader(componentType) {
  switch (componentType) {
    case ComponentDatatype.BYTE:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getInt8(
            byteOffset + i * componentTypeByteLength,
          );
        }
      };
    case ComponentDatatype.UNSIGNED_BYTE:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getUint8(
            byteOffset + i * componentTypeByteLength,
          );
        }
      };
    case ComponentDatatype.SHORT:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getInt16(
            byteOffset + i * componentTypeByteLength,
            true,
          );
        }
      };
    case ComponentDatatype.UNSIGNED_SHORT:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getUint16(
            byteOffset + i * componentTypeByteLength,
            true,
          );
        }
      };
    case ComponentDatatype.INT:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getInt32(
            byteOffset + i * componentTypeByteLength,
            true,
          );
        }
      };
    case ComponentDatatype.UNSIGNED_INT:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getUint32(
            byteOffset + i * componentTypeByteLength,
            true,
          );
        }
      };
    case ComponentDatatype.FLOAT:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getFloat32(
            byteOffset + i * componentTypeByteLength,
            true,
          );
        }
      };
    case ComponentDatatype.DOUBLE:
      return function (
        dataView,
        byteOffset,
        numberOfComponents,
        componentTypeByteLength,
        result,
      ) {
        for (let i = 0; i < numberOfComponents; ++i) {
          result[i] = dataView.getFloat64(
            byteOffset + i * componentTypeByteLength,
            true,
          );
        }
      };
  }
}

/**
 * A callback function that logs messages.
 * @callback ComponentReader
 *
 * @param {DataView} dataView The data view to read from.
 * @param {number} byteOffset The byte offset applied when reading from the data view.
 * @param {number} numberOfComponents The number of components to read.
 * @param {number} componentTypeByteLength The byte length of each component.
 * @param {number} result An array storing the components that are read.
 *
 * @private
 */
